Metal-clad waveguide sensors

Nina Skivesen

    Research output: Book/ReportPh.D. thesis

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    Abstract

    This work concerns planar optical waveguide sensors for biosensing applications, with the focus on deep-probe sensing for micron-scale biological objects like bacteria and whole cells. In the last two decades planar metal-clad waveguides have been briefly introduced in the literature applied for various biosensing applications, however a thorough study of the sensor configurations has not been presented, but is the main subject of this thesis.

    Optical sensors are generally well suited for bio-sensing as they show high sensitivity and give an immediate response for minute changes in the refractive index of a sample. Due to the high sensitivity of optical bio-sensors direct detection of biological objects is possible. The majority of optical sensors presented in the literature and commercially available optical sensors are based on evanescent wave sensing, however most of these sensors can only detect substances in the close vicinity to the sensor surface limited to below 200 nm. Bacteria and whole cells with sizes of micronscale exceed that range and thus sensors suitable for deep-probe sensing are important.

    The present thesis deals with optical, planar waveguide sensors for deep-probe evanescent wave sensing with emphasis on detection of micron-scale biological objects. I have demonstrated reversesymmetry operation using the simplest possible configuration, a freestanding glass plate acting as a multimode sensor [N. Skivesen et al, Opt. Lett. 28, 2003]. Such a sensor has only been realized by
    Qi et al [Zm Qi et al, Sens. Actuators B 81, 2002] before, however the sensing principle we present results in a broad detection range from gases to solid materials and is different from the princip.

    Metal-clad waveguide sensors are suitable for deep-probe sensing and can be operated in two different modes. I have made a thorough optimization of the waveguide parameters of both MCWG-types in terms of sensitivity [N. Skivesen et al, Sens. Actuators B 106, 2005] and [N. Skivesen et al, Opt. Lett. 30, 2005]. Each of the sensor types have previously been realized by Salamon et al [Z. Salamon et al, Biophys. J. 73, 1997] and Zourob et al [M. Zourob et al, Sens.
    Actuators B
    90, 2003] and presented for biosensing in connection with experiments, however no thorough study of the impact of the various parameters involved in the sensor configurations have been presented.

    The studied sensor configurations have been fabricated and applied for refractive index measurements and cell-detection, thus this thesis also includes presentation and analysis of experimental setups, descriptions of fabrication processes and measurements with all three sensors, where single cell detection is shown by use of the metal-clad waveguide sensors.
    Original languageEnglish
    Place of PublicationRoskilde
    PublisherRisø National Laboratory
    Number of pages109
    ISBN (Print)87-550-3467-5
    Publication statusPublished - 2005
    SeriesRisø-PhD
    Number15(EN)

    Keywords

    • Risø-PhD-15(EN)
    • Risø-PhD-15

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